Israel sees the spread of Tehran's influence in the region as a growing threat, and has carried out scores of air strikes in civil war-torn Syria against suspected military deployments and arms deliveries by Iranian forces supporting Damascus.

Iraq, which does not share a border with Israel, is technically its enemy but was last an open threat in the 1991 Gulf War. After a U.S.-led invasion in 2003 toppled Iraqi dictator Saddam Hussein, a Sunni Muslim, Israel has worried that the country's Shi'ite majority could tilt to Tehran.

Anti-Israel demonstration in Baghdad, Iraq (Photo: Reuters)

"Iraq is under growing influence of the (covert Iranian foreign operations unit) Qods Force and Iran," Major-General Tamir Hayman, the chief of Israeli military intelligence, told a conference in Tel Aviv.

With U.S. President Donald Trump signalling he sought to disengage from the region, Hayman said, the Iranians may "see Iraq as a convenient theatre for entrenchment, similar to what they did in Syria, and to use it as a platform for a force build-up that could also threaten the State of Israel."

Citing Iranian, Iraqi and Western sources, Reuters reported in August that Iran had transferred short-range ballistic missils to Shi'ite allies in Iraq. Baghdad denied the findings.

The following week, Israel said it might attack such sites in Iraq, effectively expanding a campaign now focussed in Syria.

Hayman predicted 2019 would bring "significant change" to Syria, whose President Bashar Assad has beaten back rebels with the help of Russia, Iran and Lebanese Hezbollah reinforcements, and where Trump this month ordered a pullout of U.S. troops.

"This presence of Iran, with Syria's return to stabilisation under a Russian umbrella, is something we are watching closely," he said.

Israel has also been monitoring Iranian conduct since Trump quit the 2015 nuclear deal with Tehran in May and reimposed U.S. sanctions. The deal placed caps on nuclear projects with bomb-making potential, though Iran denied having such designs. Trump, with Israeli support, deemed the caps insufficient.

"We assess that Iran will strive to stay within the deal but will do everything in order to find ways of circumventing the American sanctions," Hayman said.